Optical Properties and Energy Band Structure of Zn₃P₂and Cd₃P₂ Crystals

Abstract

Edge absorption, photoconductivity, and reflectivity spectra are investigated of Zn,P, crystals in the range from 1 to 12.5 eV and reflectivity spectra of Cd,P, crystals in the range from 1 to 12.5 eV. The Eg value of Zn,P, has been experimentally determined a t 293 and 77 OK. I t s nature has been found to be due to direct transitions. Three peaks of exciton and interband character have been observed in the photoconductivity spectrum of Zn,P, single crystals. Complex structures (about 12 peaks) have been observed in the reflectivity spectra of both compounds. Most of these structures may be accounted for in terms of the well-known theoretical calculations of their bands. Several peaks have been observed in the most thoroughly studied spectrum of Zn,P,. These peaks cannot be explained by the theoretical band scheme and are probably caused by the peculiarities of the bands of real crystals of the Zn,P, type, which have been lost in the well-known theoretical model because of the accepted simplifications of the crystal lattice.

Zn3P2–Zn3As2 Solid Solution Nanowires

“…Zn 3 P 2 , an important I I – V compound, is a p -type semiconductor with a direct band gap of 1.5 eV (at room temperature), which is in the optimal range for photovoltaic solar energy conversion. , The highest energy conversion efficiency ever reported, 5.96%, was observed for polycrystalline Zn 3 P 2 . Zn 3 As 2 ( p -type) also has a direct band gap of 1.0 eV (at room temperature) .…”

Showcasing the optical properties of monocrystalline zinc phosphide thin films as an earth-abundant photovoltaic absorber

“…S2, ESI †), at a rate of approximately 4.0 Â 10 À4 eV K À1 , consistent in magnitude with band shifts reported in the literature for zinc phosphide. 20,42,48,49 The VBM and the IB maximum would thus have different temperature dependences. This is consistent with some observations, where bands with temperature shifts of opposite signs have been observed experimentally in zinc phosphide.…”

Inter-band transitions in Zn3P2

“…The fundamental absorption edge in Zn3P2 was measured in several works. Pawlikowski et a1 (1979) presented results of absorption measurements performed on single crystals in the range 1 cm-' to 5 x lo3 cm-' and at 5,80 and 300 K. Absorption on single crystals was also measured by Fagen (1979) in the range 1 cm-' to 1.5 X lo2 cm-' at 300 K. The paper by Sobolev and Syrbu (1974) brought the absorption edge in the range of 3 cm-' to 1.5 X lo3 cm-' but this curve is displaced almost parallel towards lower energies of about 90 meV. The absorption coefficient was measured on thin Zn3P2 films in a wide energy range (up to 2.3 eV) by Fagen (1979), up to a = 7 x lo5 cm-3 and by Zdanowicz eta1 (1980) in the energy range 1.55-2.0 eV.…”